Automatic reflux head for fractionating columns



P. N. HEERE' 2,903,401

AUTOMATIC REFLUX HEAD FOR FRACTIONATING COLUMNS Sept. 8, 1959 Filed July16, 1954 spmuzwa v INVENTOR. Pirifi/ 6 55/52 B Y M2 M ///J 47' ram 5yUnited States Patent C) AUTOMATIC REFLUX HEAD FOR FRACTION- ATINGCOLUMNS Peter N. Heere, Livingston, N.J., assignor to DistillationEngineering Company, Livingston, NJ.

Application July 16, 1954, Serial No. 443,871

2 Claims. (Cl. 202-161) The invention herein disclosed relates to thecontrol of reflux in fractionating columns.

Operation of these columns requires the provision of some means forcontrolling the reflux ratio, the ratio of product taken off to that ofliquid, reflux, returned to the column.

The optimum operating condition in a column is reached when such refluxis returned at its boiling point.

Various methods have been employed, one involving removing the totalstream from the column, measuring it and returning a reheated portion asreflux. Another system has included controlling the temperature ofpartial condensers and thus condensing back portion of the vapor streamas reflux while condensing the remainder as product in a subsequentcondenser.

The boil-up rate in a column often fluctuates due to changes in feedstock, column pressure, steam pressure and other variables and since theexamples mentioned are not independent of the boil-up rate, inaccuraciesin the control of the reflux ratio have resulted.

Further inaccuracies result when the reflux is not returned exactly atits boiling point.

Controlling the reflux ratio, therefore, inside the columnproper ishighly desirable as external heat losses are prevented and because thereflux is then always returned exactly at its boiling point.

Difliculties have arisen, however, in such inside column control, sincemoving parts exposed to the leaching and corrosive action of solventvapors will often fail to operate due to lack of lubrication.

Other objections have followed from use of electrical circuits such aselectromagnetic coils around a distillation column, because of fire andexplosion hazards.

Objects of the present invention are toprovide an internal automaticreflux control unit improved to overcome objections and faults such as,mentioned, operable under either Vacuum or elevated pressures, andotherwise suited to present day requirements.

Particularly it is an object to enable moving parts to function Whileexposed to corrosive solvent vapors.

Special objects are to accomplish division of reflux and product bysimple, accurately operating mechanism and in such manner that heatlosses in the unit are minimized and compensated for with resultinghighly accurate control of reflux ratio.

Further special objects of the invention are to accomplish all of theabove in a single practical mechanical unitv applicable to various. sizefractionating towers and in which necessaryelectrical circuits will allbe enclosed and. protected in fullyexplosion-proof condition.

Other desirable objects attained by the invention and.

the novel features of construction, combination andrelation ofpartscomprising the invention are set forth or will appear in the course ofthe following specification.

The drawing accompanying and forming part ofthe specification isillustrative of a present commercial embodi'ment of 'the inventionbutstructure and arrangement may be modified and changed as regards thei'mmediate' Patented Sept. 8, 1959 illustration, all within the trueintent and scope of the invention as hereinafter defined and claimed.

Fig. 1 in the drawing is a broken vertical sectional view of theautomatic reflux head;

Fig. 2 is a top plan view of the same;

Fig. 3 is a diagrammatic view showing location of the reflux head in adistillation unit, indicating product and pressure equalizing lines;

Fig. 4 is a front elevation of the tilting funnel showing how it isflattened toward the lower end to spread the reflux in the form of aribbon.

In the construction shown in Fig. 1, vapor from the column enters thebottom of the head 7 at 8, passing around the collection box 9 andthrough the vapor slot 10 under baflle 11, leaving at the top, at 12, topass into thecondenser, the latter indicated at 13 in Fig. 3.

All the vapor is condensed in the condenser and returns by gravity asliquid to the automatic head.

This condensed liquid is diverted by baflie 1-1 and drip lip 14 to acollection pocket 15 in the upper portion of the head.

The total liquid stream flows from collector 15. through an outlet tube16 into a tilting funnel 17 which directs it either into section 18 orsection 19 of collecting box 9, the first of these delivering throughtube 20 to the column and the second through withdrawal line 21 asproduct. Sections 18 and 19 of the collecting box are shown separated bya partition plate 22.

Direction of flow is governed by position of the tilting funnel 17 whichis normally in the position shown, reflux to the column, when solenoid23 controlling the same is deenergized.

Solenoid 23 when energized lifts core 24, pulling up rod 25 connected toarm 26 on rock shaft 27 rotatingv in bearings 28. The far end of rockerarm 26 then depresses link 29 connected with arm 30 on the axle 31 whichforms the pivotal support for the funnel and which is journaled inbearings 32. This movement rocks the funnel to a position as indicatedin broken lines, Fig. l, to direct the total stream to compartment 19and out through withdrawal line 21 as product.

The reflux ratio is the ratio of time that the solenoid coil is notenergized to length of time that it is. This ratio may be determined bythe setting of the off and on interval of an electrical timer installedin series with the solenoid coil, satisfactory timers being availablefor such purpose.

In order to Withstand the corrosive action of solvent vapors theautomatic reflux head may be constructed of a resistant alloy metal.

The solenoid core 24 may be composed of iron covered with a corrosionresistant alloy sheath, as indicated at 33', or it may be constructed ofcorrosion resistant magnetic alloy. 7

The solenoid supporting tube 34 Which is extended upward from the sideof the head and which may be of resistant alloy metal, is indicated asequipped with cooling'fins 35 to prevent overheating of the solenoidwhen the automatic head is operating at high temperatures.

The solenoid housing 36 may be constructed With a removable cap 37 in anapproved explosion-proof, Class I, Group D manner suitable for operationof electric circuits in a hazardous location.

The enclosure cap 37 is shown carrying a stop or. pro jection 38. Parts36, 37 and 38" are preferably constructed of iron or various alloysadapted to be readily magnetized and demagnetized. The use of suchmetals. and stop 38. considerably increases the strength of the magneticfield around solenoid coil 23'.

graphite, this material being corrosion resistant to most" however, thatthese hearings may be of other corrosion resistant materials such asplastics in the nature of ileflon. polytetrafluoroethylene, preciousmetals and the The entire funnel and bearing supports are shown mountedon a plate 39 removably seated in the bottom of the condensatecollecting chamber 15 so as to be readily removable. for inspection,cleaning or servicing.

The amount of travel of the tilting funnel is controllable in theillustration by adjustment of the length of theconnecting link 25, thisbeing shown as having a regulatable screw thread engagement at 40 in theend of the core 24.

The complete solenoid housing including outer portions of the supportingtube 34, are shown located outside of the column insulation and these,with the cooling fins 35, will condense vapors that reach up into theseparts. The condensate which may thus form will be collected, togetherwith liquid that flows down from the condenser in the collecting pocket15 and thus be accurately divided by the tilting funnel.

The collecting box 9 is shown located well within the shell of thereflux head with a minimum cross-sectional area of metal present forconduction of heat away from the box, thus minimizing condensation ofvapor and any loss of accuracy of reflux ratio. This is furtherfacilitated by small cross-section of supporting struts 41 and minimumcross-section of withdrawal tube 21. The box itself, as shown, does nottouch the shell of the reflux ead.

Since the pressure of the vapor in the automatic reflux head may besomewhat higher than that at the top of the condenser 13, Fig. 3, it maybe necessary or desirable to have an equalizing line 42 extendingbetween the product outlet 21 and the condenser vent 43, and also a sealloop 44 in the product line, the latter to prevent vapor from blowingout through this line. The height of this seal loop should be suflicientto hold back vapor when the column is operating at maximum contemplatedrate.

The invention provides a practical automatic reflux head in the form ofa unit adapted for direct mounting in the column of large and smalldiameter fractionating towers. This unit may be readily constructed ofavailable plate, pipe, tubing and other forms of metallic, ceramic,plastic or other materials. The adjustable mechanical linkage providesfor accurate reflux ratio control. The parts particularly subjected tocorrosive action are carried by a plate or base readily removable forinspection, cleaning or repair.

The graphite bearings provide corrosion resistant and self-lubricatingsupport for parts operating in the corrosive atmosphere. The electricalparts are completely enclosed and protected against hazardous explosiveconditions.

Heat losses in exposed parts are compensated for by collecting condensedmaterial and conducting it back into the main liquid stream for accuratedivision, resulting in a higher degree of accuracy in reflux ratiocontrol.

The internal collecting box is so arranged that any heat losses from itto the wall of the reflux head are minimized, with resulting higheraccuracy in reflux ratio control. The adjustable core of the solenoidsheathed with protective alloy, is unaffected by corrosive solventvapors.

While shown equipped with cooling fins, water or other cooled jacket maybe provided on the solenoid tube to protect the solenoid from hightemperatures such as sometimes may be present in the automatic refluxhead.

The solenoid housing constructed of magnetic material and whollyenclosed, provides ample magnetic strength for the solenoid operationdescribed.

The automatic reflux head disclosed is especially adaptable to vacuum,pressure or hazardous service, since no stufling boxes or otherpotential leak sources are present in the construction.

What is claimed is:

1. A variable ratio automatic reflux head unit for assembly with afractionating column comprising an openended upright cylindrical shellof a diameter corresponding to that of the column, said shell havingmeans at its upper and lower ends for connecting same to the top of thecolumn and to a condenser above the column to carry the complete boil-upfrom the column to the condenser; a collection box supported in thelower portion of the shell in substantially transverse relationshipthereto and in spaced relation to the wall of said shell, saidcollection box having a substantially vertical partition mounted thereinto separate same into separate reflux and product compartments, thereflux compartment having a vertical discharge outlet in the bottomthereof to discharge reflux collected therein directly into the columnwhen the unit is in assembled relationship therewith, the productcompartment having a laterally extending outlet immediately adjacent itsbottom to permit the carry off of the collection product, a liquidreceiving pocket transversely mounted in the upper portion of the shelland spaced above said collection box, the bottom surface of said liquidreceiving pocket being provided with a discharge outlet which issubstantially in vertical alignment with the partition of saidcollection box, downwardly extending tilting funnel means journaled atits upper end to the undersurface of said pocket and in registry withthe discharge outlet present therein with the lower end of said funnelmeans terminating at said collection box at a point above said partitiontherein, said funnel means having a swinging movement to carry liquidfrom the liquid receiving pocket to the reflux and product compartmentsat opposite sides of said partition, an inwardly extending anddownwardly inclined bafile plate secured to the wall of said shell abovethe plane of said liquid receiving pocket and extending inwardly fromthe wall of the shell and terminating at a point above and over saidliquid receiving pocket and forming a vapor slot therewith for passingvapors over the pocket, and electromechanical means mounted externallyon the sidewall of said shell and operatively connected with saidtilting funnel means to actuate same to eifect the desired tiltingoperation and to vary the arc of swinging movement of the funnel meanswhereby reflux and product are developed from the total vapor flow fromthe column and reflux is returned to the column at boiling pointunaffected by external conditions and a substantially constant refluxratio is maintained essentially independent of external heat losses.

2. A variable ratio automatic reflux head unit for assembly with afractionating column comprising an openended upright cylindrical shellof a diameter corresponding to that of the column, said shell havingmeans at its upper and lower ends for connecting same to the top of thecolumn and to a condenser above the column to carry the complete boil-upfrom the column to the condenser; a collection box supported in thelower portion of the shell in substantially transverse relationshipthereto and in spaced relation to the wall of said shell, saidcollection box having a substantially vertical partition mounted thereinto separate same into separate reflux and product compartments, thereflux compartment having a vertical discharge outlet in the bottomthereof to discharge reflux collected therein directly into the columnwhen the unit is in assembled relationship therewith, the productcompartment having a laterally extending outlet immediately adjacent itsbottom to permit the carry ofi of the collection product, a liquidreceiving pocket transversely mounted in the upper portion of the shelland spaced above said collection box, the bottom surface of said liquidreceiving pocket being provided with a discharge outlet which issubstantially in vertical alignment with the partition of saidcollection box, downwardly extending tilting funnel means journaled atits upper end to the undersurface of said pocket and in registry withthe discharge outlet present therein with the lower end of said funnelmeans terminating at said collection box at a point above said partitiontherein, said funnel means having a swinging movement to carry liquidfrom the liquid receiving pocket to the reflux and product com-ipartments at opposite sides of said partition, an inwardly extending anddownwardly inclined baflle plate secured to the wall of said shell abovethe plane of said liquid receiving pocket and extending inwardly fromthe wall of the shell and terminating at a point above and over saidliquid receiving pocket and forming a vapor slot therewith for passingvapors over the pocket, said baflie plate terminating in a drip lip oversaid pocket, and a solenoid supported externally on the sidewall of saidshell, a core operable by said solenoid and operating connectionsextending from said core to said tilting funnel means adjustable to varythe arc of swinging movement of the funnel whereby reflux and productare developed,

from the total vapor flow from the column and reflux is returned to thecolumn at boiling point unafiected by external conditions and asubstantially constant reflux ratio is maintained essentiallyindependent of external heat losses.

References Cited in the file of this patent UNITED STATES PATENTS1,953,939 Jones Apr. 10, 1934 2,129,502 McCreary Sept. 6, 1938 2,218,624Robertson Oct. 22, 1940 2,251,185 Carter et a1. July 29, 1941 2,518,574Skopecek Aug. 15, 1950 2,556,752 Galstann et al. June 12, 1951 2,573,807Piros et a1. Nov. 6, 1951 2,591,010 Rollins et al Apr. 1, 1952 2,601,971Todd July 1, 1952

1. A VARIABLE RATIO AUTOMATIC REFLUX HEAD UNIT FOR ASSEMBLY WITH AFRACTIONING COLUMN COMPRISING AN OPENENDED UPRIGHT CYLINDRICAL SHELL OFA DIAMETER CORRESPONDING TO THAT OF THE COLUMN, SAID SHELL HAVING MEANSAT ITS UPPER AND LOWER ENDS FOR CONNECTING SAME TO THE TOP OF THE COLUMNAND TO A CONDENSER ABOE THE COLUMN TO CARRY THE COMPLETE BOIL-UP FROMTHE COLUMN TO THE CONDENSER; A COLLECTION BOX SUPPORTED IN THE LOWERPORTION OF THE SHELL IN SUBSTANTIALLY TRANSVERSE RELATIONSHIP THERETOAND IN SPACED RELATION TO THE WALL OF SAID SHELL, SAID COLLECTION BOXHAVING A SUBSTANTIALLY VERTICAL PARTITION MOUNTED THEREIN TO SEPARATESAME INTO SEPARATE REFLUX AND PRODUCT COMPARTMENTS, THE REFLUXCOMPARTMENT HAVING A VERTICAL DISCHARGE OUTLET IN THE BOTTOM THEREOF TODISCHARGE REFLUX COLLECTED THEREIN DIRECTLY INTO THE COLUMN WHEN THEUNIT IS IN ASSEMBLED RELATIONSHIP THEREWITH, THE PRODUCT COMPARTMENTHAVING A LATERALLY EXTENDING OUTLET IMMEDIATELY ADJACENT ITS BOTTOM TOPERMIT THE CARRY OFF OF THE COLLECTION PRODUCT, A LIQUID RECEIVINGPOCKET TRANSVERSELY MOUNTED IN THE UPPER PORTION OF THE SHELL AND SPACEDABOVE SAID COLLECTION BOX, THE BOTTOM SURFACE OF SAID LIQUID RECEIVINGPOCKET BEING PROVIDED WITH A DISCHARGE OUTLET WHICH IS SUBSTANTIALLY INVERTICAL ALIGNMENT WITH THE PARTITION OF SAID COLLECTION BOX, DOWNWARDLYEXTENDING TILTING FUNNEL MEANS JOURNALED AT ITS UPPER END TO THEUNDERSURFACE OF SAID POCKET AND IN REGISTRY WITH THE DISCHARGE OUTLETPRESENT THEREIN WITH THE LOWER END OF SIAD FUNNEL MEANS TERMINATING ATSAID COLLECTION BOX AT A POINT ABOVE SAID PARTITION THEREIN, SAID FUNNELMEANS HAVING A SWINGING MOVEMENT TO CARRY LIQUID FROM THE LIQUIDRECEIVING POCKET TO THE REFLUX AND PRODUCT COM-